Orthogonal Frequency Division Multiple Access (OFDMA) technology is getting very popular in modern communication systems since the OFDMA technology can efficiently support multiple mobile stations with limited bandwidth and easily provide Quality of Service (QoS). The OFDMA technology is a multiple access version of orthogonal frequency-division multiplexing (OFDM). OFDM is a modulation technique for data transmission based on frequency-division multiplexing (FDM), which uses different frequency channels to transmit multiple streams of data. In OFDM systems, a wide channel is divided into multiple narrow-band subcarriers, which allow orthogonal modulated streams of data to be transmitted in parallel on the subcarriers.
In OFDMA systems, multiple subscribers can simultaneously use different subcarriers for signal transmission. Thus, in an OFDMA system, multiple data bursts can be transmitted from a base station to multiple mobile stations in the same time frame but allocated in different frequency subcarriers. Consequently, an OFDMA system can support multiple mobile stations using different subcarriers.
Since OFMDA systems are wireless communication systems, the transmitted signals experience multi-path fading and delay across the system bandwidth due to what is commonly referred to as signal channels. In order to compensate for the effects of these signal channels, OFDMA receivers perform channel estimations using pilot signals embedded in the transmitted signals. Since the pilot signals are known signals, channel estimates for the pilot signals can be derived. Using the channel estimates for the pilot signals, channel estimates for data signals can be extracted by interpolation. If there is significant error in the resulting channel estimates, the received data will be erroneously decoded. In other words, the original modulation symbol will be decoded in error if there is significant error in the channel estimation because each subcarrier in the OFDMA symbol is multiplied by a different fading coefficient that has a unique amplitude and phase. This is especially true for higher-order quadrature amplitude modulation (QAM), such as 16-QAM and 64-QAM, which is used to transmit high data rate signals.
In OFDMA systems, OFDMA signals may have different pilot subcarrier spacing within one OFDMA symbol or between different OFDMA symbols. In order to process OFDMA signals with variable pilot subcarrier spacing, multiple interpolation schemes may be needed to derive data channel estimates from pilot channel estimates having different pilot subcarrier spacing, which require significant design and maintenance demands, as well as large receiver memory.
Thus, there is a need for a device and method for performing channel estimation for an OFDM-based wireless communication system with variable pilot subcarrier spacing that reduces design and maintenance demands, as well as receiver memory.